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SR560 OFFSET ADJUSTMENT PROCEDURE
Equipment needed:
Digital volt meter
Oscilloscope
4 BNC cables
1 BNC tee
Function generator
Small slotted screwdriver
Phillips screwdriver
Remove bottom cover of SR560 to expose component side of pc board.
1. Turn SR560 off. Hold down "Reset" button, and turn unit back on
(this sets unit back to default setting).
2. Using a Digital Volt Meter, adjust front panel offset pot (located between "A'' and "B" input
BNC's on front panel) to read zero volts from pin 14 of U407 to gnd (output BNC shield). Do
not use chassis as ground.
There are 4 potentiometers located on the bottom right side of pc board
(looking at component side, with front panel facing forward)
P104 = low gain offset adjust
P101 = low gain CMRR adjust
P103 = high gain offset adjust
PIOZ = high gain CMRR adjust
3. Set coupling to "GND" and gain = 50,000.
4. Adjust P103 for zero volts on 50 ohm output, using scope.
5. Set gain = 1000 and Source to "A-B''.
6. Set function generator to square wave, Freq = 1Khz amplitude = 500mV pp.
7. Using BNC tee, and 3 bnc cables, input square wave into channels A and B.
8. Set coupling to "DC".
9. Adjust P102 to null square wave on the scope.
10. Set coupling to "GND" and gain = 50,000
11. Readjust P103 for zero volts on scope.
12. Set gain = 50 and coupling to "DC".
13. Set scope to AC coupling.
14. Using the Digital Volt Meter measure the voltage from pin 6 of U105 to ground (output bnc
shield).
15. Adjust P104 for zero volts on meter.
16. Adjust P101 to null square wave on scope.
You might have to readjust P104 and P101 several times. The end result should be zero volts
on pin 6 of U10$ with the smallest square wave that you can adjust on the scope.